The present invention relates to printers, and more specifically to a system for delivering ink to an ink jet print head. Unlike other systems, this system can measure and control the pressure of ink in a reservoir that is directly connected (that is, without tubes) to the print head. The direct connection ensures that there are no additional pressure swings at the print head, which is important because the pressure needed for proper meniscus control is a very small, slightly negative pressure, and should preferably be measured and controlled in about 30 ms.
Some other ink jet systems maintain pressure by measuring the pressure of air that is in fluid communication with the ink near the print head, or they rely on a combination of ink or air pressure and keep the ink reservoir at a fixed height relative to the print head. In whatever combination that might be used in such systems, there are problems associated with having the ink exposed to air in the system, and with the necessity of maintaining a fixed height of the ink column above or below the print head.
It should be understood that the drawings are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the inventions described and claimed herein or which render other details difficult to perceive may have been omitted. It should be understood, of course, that the inventions described herein are not necessarily limited to the particular embodiments illustrated.